Hydraulic shock absorber with flexible reservoir



Oct. 4, 1955 2,719,611 c. M. L. L.. BoURclER DE CARBON DE PREVINQUIERES HYDRAULIC SHOCK ABSORBER WITH FLEXIBLE RESERVOIR Filed Jan. 18, 1950 United States Patent .12,719,611 HYDRAULIC snoer; nnsoRBER-wrrnrrnxmrn 'REsERvom Christian Marie Lucien Louis Bourcier de Carbonde Prvinquires, Paris, France Application Januaryf18, 1950, Serial No. 139,284 Claims priority, v.application France 'January 19, A1949 l3 Claims. (Cl.'188-`88) This invention relates 4`to"hydra1'1`lic shock-absorbing apparatus, and vmore lparticularly Ato shokrabsor'bers of the telescopable type.

Among the most difcuitprdblems encountered fin 1 the design of :hydraulicshockabsorbers`of 'the above-defined type is that -of'providing Acompen'sati'onforfthe -vvolume of the Y'piston-rod. 0n 'the kone "hand, Yit l"is necessary that the piston-rod be fully lteles'oopable finto lthe ioper-ating cylinder 'of the shoks'absoiberJduring-:the cor'1tr-a'etion stroke thereof, A:and 'on "the/'other lha-nd it "iv-necessary to prevent the occurrence of-'cavitation f'ffects. "Since oil is an incompressible l`liuid`-t`o all A"pir'facti'crzrl purposes, it becomes necessary, lifbothfthe above"conditionslare-fto-be fulfilled simultaneously, to provide acompensating 2capacity located outside*theTopera-ting cylinder in "which the piston operates.

In the drawingj'lligs. 1,72 and 3 arelsectio'nal views `of three forms -of shockbsorbing appara-tus.

In the'rnajority lc'f1"curre11ttelescopic lshoelc-abso'r`bers, such compensating 'capacityV is 4`Iprovided l infthe ""'form fof an Aannular 'space 'A l(see Tig. 'l-o thefaccompany-in'g drawing) defined between thel'operatingfcylinder C and a further *and* outer -metallie'cylinder lB,"said spacci-being partially lled by'theoperatingluid and communicating at its lower 'end with ntheoperating cylinder.

The ,provision o'f "thetwocylindersf andtC complicates the apparatus and increases litsf-cost, but1-above=allflthe conventional arrangementjust ieseribdlo'ffers la lserious functional drawback in "that the 'partly illled annular capacity A is rigidly v.connected with --a Wheel-fof the vehicle on which the shokabsoberis mountedywhereas the piston is rigid withiiheramefof-said`vehicle. The movements of the wheel are excessively violent, so that the acceleration 'factor' 'canfrequently greatly uexceed that of gravity. As 1a result, iur'ing rnotion'ot` the vehicle, the oil -contained in the annular icapacity A is :strongly agitated and does not constantly remain at the'bottom or said capacity, being only retained atthe bottom ratrest by gravity. Consequently, during the suction .stroke which, theoretically, should causepartof the 'oil to pass from the capacity A into the operating` cylinder space, what actually is drawn into the operating cylindernis-` not necessarily oil, but sometimes-air .andtirnosbfrequently a mixture -or-ernulsion of air andgo'il. vrl`hus part =of` the air contained in the capacity A is drawn into the operating cylinder, whichis Vextremely objectionable in respect to proper 'operation Aof .the apparatus. fFor, invthe Ifirst place, the emulsion alters the physical characteristics of the operating iiuid oil, and, worse still, the ingress of air into the operating space creates cavitation phenomena which are very objectionable from the standpoint of comfort of the vehicles occupants.

In a co-pending U. S. patent application Serial No. 22,836 filed April 23, 1948, now abandoned, I have suggested connecting the piston with the wheel rather than with the frame of the vehicle, and providing the compensating capacity in the form of a chamber S (see Fig. 2) within the operating cylinder and above the useful :space thereof wherein L:the piston operates. fSueh -con- 'struction `practically 'completely eliminates lthe `a'-bovede scribed l drawbacks "because fthe compensatingcapacity 'lis now connected with the frame ratherfthanthe Wheel and the vertical accelerations to which-theffr-ameiissub- However adrawback --of zthe arrangem'ent just 'described lis tha'tfthe useful strokefoffthe piston is" considerably reduced `for la g-iven'limited -value fof Itho-spacing lbtlween theaxes andW. v

It is an object of this Linvention f to -solve tthe abovedened problem Ain a fnew and improved Iman-ner 'which substantially does away \wi'th21the :limitation :'just imontioned. For this purpose ="I essentiallyI fprovlide Utl-1e f compensating capacity inl the Aiform fof 'fan expansible-lcapacity associated with thelrnainlfor operating:cylindencapacity.

l-The said -expansible Vcapacity :ma-y among yother .possible-@construction `be defined by-LaI suitable lasticshe'etmaterial-impervious'to oil, suchas synthetic rubber.

IInfone form of embodiment which rincludesuafpiston mounted on 'the I`wheel rand acylindersconnectecl wilththe fframe,theielas'ticwaIlfof thea-capacityfis desir-ably arranged fat fthe Lend o'f said-cylinder opposite fthe :end

through `which the piston-rodextcnds.

fway of i example and fito Lprovide a aftuller funderstanding 'of 'the invention, :one 'exemplary yembodiment thereof is villustrated -in Figure .-3 :of theaccompaarrying drawing.

In -this ertrbo'dirnent my.improved:shockfabsorbertoomprises ay lcylinder 1in-which' is movable laepistonainfori-'ned withea-i-restricted 'duct4"therethroughfto allow anrestrioted llow of 'iluid through the piston. The "piston f3 risf-conneetedwiththe 'Wheel-'by a tpistonlrodtfthroughf. asuitableffconnector"51and the :cylinder Il "is conneetedi'with thefvehicle frame' byai connector! Zirigid :with :th'ei'oylinder head'7.

The compensating capacity T 'iis'.deined fbyfatn-.iexpansible sheet member I-E, i=suchr1as syntheticrulber. or any other suitable Velastic :material impervious ato faoil. l'I'hesheotmember 'E fisseale'd as at V 'aarotrnd thefcoznneot'or Vsh'airkfand `at roverlthe cylinder 'ihea'd Such sealed attachment may .be. effectedtby y'making .use of fthe inherent 'elasticity of'lthe'rubberllikewmateriaL .the .rends V and -W thereof "beingrsuitablylthickened :fas fshown, and/for fbyl providing `suitable- :external *clampingA rings=or the'like. t

As "shown in'Fig. 3,'a valve F wsuchsaszan zttssornblI comprising av ball :and alcoil Yspring ofi-suitablestrength'to oppose forcesbelow Ia predetermined'value, is provided so that the-'volume of `o'il'forced into the capacityT will at no time `exceed vthe famount strictly knecessary =tojust compensate -for the volume of the .'pistonrod. AVfil'tis draw-n 1in linto fthe operatingL'cylinder'throughja "zero loading type of check-valvelformedfor yexamplefby an annular 'strip -of metal foilK lof-verythincgagegadapted 1to .alternately seal andV uncover ports :i andl j fasfthefpiston moves towards `rand awayrfrom'the fcapacity IT, respectively.

The above-described :construction makes :it possible to make use of the fullavailable length"ofstrokefiornthepiston within ithe loperatingicylinderprnoreover, it isr'extrornetly-"eTfec"ti1ve inl preventing thepreviouslyedescribed'naxnulsion and cavitation effects, since in no portion of its circuit does the oil come into contact with air. Finally, the construction described herein makes it possible if desired to return to the more conventional arrangement in which the piston is connected with the frame rather than with the wheel of the vehicle, an arrangement in which it is easier to afford adequate protection for the piston rod.

In a modification of the present invention, I may use a tubular rod and house the expansible capacity T at the #Patented Oct. 4, 1955 free end of the piston rod, it being understood that between the capacity and the operating cylinder space there would be interposed a suitable assembly such as that comprising the valve F and the check-valves i and j described above in connection with Fig. 3, such a valve assembly being of course essential for proper operation of the compensating capacity.

What I claim is:

1. A direct acting shock absorber for controlling the relative movements of a sprung member and an unsprung member comprising, in combination, two telescoping members comprising respectively a cylinder and a piston slidably mounted within said cylinder, the piston having a piston rod rigid therewith and extending through an end of said cylinder to the exterior thereof, means or connecting one of said members to said sprung member and means for connecting the other of said members to said unsprung member, whereby upon relative movement of said members the piston will reciprocate in said cylinder, a working liquid in said cylinder and means for bypassing said liquid from one side of the piston to the other as the latter reciprocates in said cylinder, means for compensating for the displacement of liquid from the cylinder by the periodic entrance of additional portions of the piston rod into the cylinder during operation, said last named means comprising an expansible and contractible sac of flexible and elastic material having a mouth secured about the end of said cylinder opposite the end through which said piston rod passes, at least two openings through the end of the cylinder enveloped by said sac, provided for the passage of working liquid between the interior of said sac and the interior of said cylinder at one side of the piston, pressure actuated valves controlling ow through said respective openings, the valve controlling flow from the cylinder to said sac being the more resistant to flow than the valve controlling ow in the opposite direction, said sac being disposed entirely exteriorly of the cylinder and of all parts of said shock absorber, whereby it is subject externally only to the pressure of the circumambient atmosphere.

2. A direct acting shock absorber for controlling the relative movements of a sprung member and an unsprung member comprising, in combination, two telescoping members comprising respectively a cylinder and a piston slidably mounted Within said cylinder, the piston having a piston rod rigid therewith and extending through an end of said cylinder to the exterior thereof, means for connecting one of said members to said sprung member and means for connecting the other of said members to said unsprung member, whereby upon relative movement of said members the piston will reciprocate in said cylinder, a working liquid in said cylinder and means for by-passing said liquid from one side of the piston to the other as the latter reciprocates in said cylinder, means for compensating for the displacement of liquid from the i cylinder by the periodic entrance of additional portions of the piston rod into the cylinder during operation, said last named means comprising an expansible and contractible sac of flexible and elastic material having a mouth secured about the end of said cylinder opposite the end through which said piston rod passes, at least two openings through the end of the cylinder enveloped by said sac, provided for the passage of Working liquid between the interior of said sac and the interior of said cylinder at one side of the piston, pressure actuated Valves controlling flow through said respective openings, the valve controlling ow from the cylinder to said sac being the more resistant to ow than the valve controlling iiow in the opposite direction, said sac and the interior of said cylinder both being full of Working liquid at all times to the exclusion of air or any emulsion-forming gases, said sac being disposed entirely exteriorly of the cylinder and of all parts of said shock absorber, whereby it is subject externally only to the pressure of the circumambient atmosphere.

3. A direct acting shock absorber for controlling the relative movements of a sprung member and an unsprung member comprising, in combination, two. telescoping members comprising respectively a cylinder and a piston slidably mounted within said cylinder, the piston having a piston rod rigid `therewith and extending through an end of said cylinder to the exterior thereof, means for connecting one of said members to said sprung member and means for connecting the other of said members to said unsprung member, whereby upon relative movement of said members the piston will reciprocate in said cylinder, a working liquid in said cylinder and means for bypassing said liquid from one side of the piston to the other as the latter reciprocates in said cylinder, means for compensating for the displacement of liquid from the cylinder by the periodic entrance of additional portions of the piston rod into `the cylinder during operation, said last named means comprising an expansible and contractible sac of iiexible and elastic material having a mouth secured about the end of said cylinder opposite the end through which said piston rod passes, at least two openings through the end of the cylinder enveloped hy said sac, provided for the passage of working liquid between the interior of said sac and the interior of said cylinder at one side of the piston, pressure actuated valves controlling iiow through said respective openings, the valve controlling flow from the cylinder to said sac being the more resistant to flow than the Valve controlling ow in Athe opposite direction, said sac and the interior of said cylinder both being full of working liquid at all times to the exclusion of air or any emulsion-forming gases, said sac being disposed entirely exteriorly of the cylinder and of all parts of said shock absorber, whereby it is subject externally only to the pressure of the circumambient atmosphere, a rigid stem having one end xed to the end of said cylinder to which said sac is applied and extending through a sealed opening approximately centrally of said sac and provided with means at its outer end for securing it to one of said members.

References Cited in the file of this patent UNITED STATES PATENTS 1,304,311 Heldrich May 20, 1919 1,457,122 Ree May 29, 1923 1,825,233 Joyce Sept. 29, 1931 2,149,040 Binder et al. Feb. 2S, 1939 2,314,404- Katcher Mar. 23, 1943 2,357,278 OConnor Aug. 29, 1944 2,410,176 Magrum Oct, 29, 1946 2,417,504 Knaggs et al. Mar. 18, 1947 2,571,279 Myklestad Oct. 16, 1951 FOREIGN PATENTS 331,444 Italy Nov. 6, 1935 

